The objectives of this study was to investigate the biomechanical causes of hydroxyapatite (HA) coated blade implant fracture. The fractured surface of a broken implant was observed by SEM, which indicated that the fatigue crack started at the distal portion and developed to mesial portion. The fatigue test of the HA coated blade implant showed about 25 kgf/mm2 of fatigue strength. The results of threedimensional Finite Element Analysis (3D-FEA) indicated that the fracture of clinical case No.5 was suspected to be due to the repeated vertical load on the tooth.
